Swallow Prominent Pheosia tremula
Wingspan 45-55 mm.
Similar to Lesser Swallow Prominent, though not necessarily larger, this species has a noticeably longer and narrow white tornal triangular streak than that species. It also differs in having a fine whitish line running through the dark blotch in the tornal region.
It is fairly common throughout Britain, and flies between May and July, with two broods in the south.
The larvae feed on poplar (Populus) and sallow (Salix).